Stabilized thermoplastic cellulose ether composition



Patented Dec. 26, 1950 UNITED STABILIZED THERMGFLASTIC CELLULOSE ETHERCOMPOSITION William Koch, Wilmington, DeL, assignor to Hercules PowderCompany, Wilmington, DeL, a-

corporation of Delaware No Drawing. Application Scptern'berZS, 1948,Serial No. 51,325

10 )laims. (o1. 106-"-176) This invention relates to the stabilizationof cellulose ethers and, more particularly, to the production ofcellulose ethers and their compositions which retain their viscosity andgood color during and after exposure to heat, light, oxidation,weathering and other degrading infiuences.

Cellulose ether compositions and particularly ethyl cellulosecompositions have found considerable usefulness where the properties oftoughness, dimensional stability and flexibility at extremely lowtemperatures are desirable. However, when subjected to elevatedtemperatures, prolonged exposure to ultraviolet light or aging ingeneral, there has been a discoloration and/or viscosity degradationwhich has limited their usefulness to a considerable extent. Thus,compositions depositing a colorless mass from solution have givenrelatively dark amber masses much like tortoise shell upon being moldedat temperatures of the order of 200-300 C. In addition, there has beenconsiderable loss of viscosity, i. e., degradation, leading to brittlemolded products. Similar discoloration and lossof viscosity, strength,and flexibility also result from prolonged storage or exposure toultraviolet light and weathering. The problem of stabilization isparticularly dimcult where relatively highheats are required, as in fastmolding, or when the material is exposed. for prolonged periods tosevere weathering conditions.

In the past, viscosity stabilization has been effected to some extent bythe addition of cer tain amines and certain phenolic bodies. In mostcases these have tended to add color themselves or have contributed tothe formation of treme loss of viscosity that a relatively uselessvmolded product results. Even mildly bleaching, slightly acidic agents,such as sulfur dioxide, have been found tov cause crazing, scorched darkspots, brittleness; i. e., local or general degradation at moldingtemperatures of 209 C.,. and above, either immediately or on normalaging. As a. result, it has not been possible to prepare clear,colorless, molded ethyl cellulose articles Where such improve-.

or even to prepare molded ethyl cellulose articles Ethyl cellulosemolded in pale orpastel shades. articles have, therefore, been made onlyin pigmented or dark colors.

Now, in accordance with this invention, it has been found that ethylcellulose and other thermoplastic cellulose ethers and theircompositions may be eifectively stabilized against discolora tion andviscosity degradation, when exposed to heat and weathering, by adding toor incorporating with the cellulose ether a small amount ofp-sec-amylphenol, alone or in combination with a sulfurdioxide-producing compound. When 1 used alone, the p-sec-amylphenolexerts a very definite stabilizing effect on cellulose ethers and. theircompositions, protecting them from dis,v

coloration and degradation when exposed to heat,

light, air, weathering and other degrading in- Optimum results areobtained, howevenwhen the psec-a1nylphenol is used in combination withsmall amounts of a sulfur dioxideproducing compound. Thus, in accordancewith this invention, cellulose ethers and their compositions may bemolded at elevated temperatures such as.200 Caand above to form tough,

"shaped articles very greatly improved'in color after molding ascompared with previous molded tively colorless moldings and moldings inlight,

and pastel shades.

In view of the acidic nature of sulfur dioxide 1 and in view of the factthat phenolic bodies are, in general, of an acidic rather than basicnature, it is surprising and unexpected that the use of p-sec-amylphenolalone or in combination with sulfur dioxide in cellulose ethercompositions at, molding temperatures brings about formation oftough,'-undegraded' products of improved color.

Heretofore, it has been the experience in this field that acids causedsevere degradation, sometimes accompanied by discoloration, whencellulose ethers were exposed to heat or aged. thermore, althoughconsiderable improvement in stability characteristics and particularlycolor are obtained by the use of p-sec-amylphenol alone, it has beenfound that optimum stability improvement is obtained whenp-sec-amylphenol and a sulfur dioxide-releasing compound are used incombination.

which follow. All parts and percentages given are by weight.

EXAMPLE 1 Ethyl cellulose having 46.8% to 48.5% ethoxyl content and 100cps. viscosity was dissolved in 80:20 toluene:alcohol. p-sec-Amylphenolwas added to a portion of the solution to give a composition containing1% p-sec-amylphenol, based on the weight of the ethyl cellulose. Filmsabout 3 mils in thickness were then cast from the composition, andportions of the films thus formed were heated for 48 hours at 120 C. inair. Films of the ethyl cellulose containing no stabilizer were alsoheated under the same conditions. Viscosities of the samples before andafter heat treatment were determined and from these figures theviscosity retention was obtained. Flexibility and discoloration werealso noted. Table I below compares the results obtained with thestabilized and unstabilized ethyl cellulose.

TABLE I Eoaluation of p-sec-amylphenol as stabilizer for ethyl celluloseafter heating for 48 hours at 120 C. in air Per Cent Sample FlexibilityDiscoloration Viscosity Retention Unstabilized Flexible Very slight. 27.3 p-sec-Amylphenol (1%) do do 78.

TABLE II Evaluation of p-sec-amylphenol as stabilizer for ethylcellulose after exposure in the Fade- Ometer for 50 hours Per CentSample Flexibility Discoloration Viscosity Retention UnstabilizerlBrittle p-sec-Amylphenol (1%) Flexible...

These data illustrate that a small amount of p-sec-amylphenol in anethyl cellulose film which is exposed 50 hours in the Fade-Ometereffectively stabilizes the ethyl cellulose with respect to both filmflexibility and viscosity retention.

EXAMPLE 2 The following ingredients were colloided on a two-roll mill at290-310 F. for 20 minutes, dried, chipped into a molding powder, andmolded into discs at 400 F. for minutes.

Parts Ethyl cellulose (44.5 to 45.5% ethoxyl, 100

cps. viscosity) 85 Dibutyl phthalate Similar compositions were preparedand molded containing (1) 2% p-sec-amylphenol, (2) 0.3% butadienesulfone, and (3) 2% p-secamylphenol and 0.3% butadiene sulfone.

All samples were exposed to the Sl sun lampfog box cycle (2 hours in thefog chamber, 2 hours irradiation under the S-l lamp, 2 hours in the fogchamber, 18 hours irradiation) for hours. Color of discs after moldingand color and condition of discs after exposure to 8-1 sun lamp-fog, boxcycle were determined and are set forth in Tables III and IV below.Colors were measured on the spectrophotometer, and values are expressedas luminous transmittance and as the red trichromatic coefficient. Theformer value represents the amount of light that each disc willtransmit, and the red coefficient represents the per cent of red in thetotal color value of the sample.

TABLE III Color of discs after molding (spectrophotometer) LuminousTricbgl- Q Transmitmatic o- Sampl tanc efficient Per Cent (Red)Unstabilized 2.0 6139 2% p-sec-Amylphenol 15.8 .5082 0.3% Butadienesulfone 12.1 .5289 2% p-sec-Amylphenol and 0.3% utadiene sulfone l8. 94876 TAB E IV Color and condition of discs after exposure to S-1 sunlamp-fog boa: cycle (spectrophotometer color values) A higher percentagevalue for luminous transmittance in the tabulated data signifies betterclarity with more total light being transmitted through the sample thana lower value signifies. A lower value for the red trichromaticcoeificient in the tabulated data signifies less red in the total colorvalue of the sample and therefore a more nearly colorless sample. Thus,these data illustrate that ethyl cellulose plastic discs containing asmall amount of p-sec-amylphenol alone or in combination with butadienesulfone transmit a great deal more light and show much better resistanceto discoloration than an unstabilized ethyl cellulose plastic disc, bothimmediately after molding and after exposure for 120 hours to the 8-1sun lamp-fog box cycle. Fur thermore, the surface condition of ethylcellulose plastic discs containing a small amount of p-sec-amylphenolalone or in combination with butadiene sulfone was in much bettercondition than either the unstabilized ethyl cellulose disc or. theethyl cellulose disc containing butadiene sulfone alone. The surface ofthe ethyl cellulose discs which did not contain any p-sec-amylphenol wasbadly crystallized and disintegrating incontrast to a fine crazingwithout surface disintegration or crystallization for the ethylcellulose discs containing a small amount of p-secamylphenol. 2

EXAMPLE 3 To 175 grams of flake ethyl cellulose containing 0.35% byweight of butadiene sulfone was added 62 grams of dibutyl phthalate and7 grams of p-sec-amylp'henol, and the mixture was placed on a two-rollmill with the rolls at 310:10 F. with the mill running, an additional1'75 grams of the'same flake-ethyl cellulose was added and the materialwas milled" at 300 to 320 F. for minutes. The composition was thenstripped from the rolls'as a well-colloided plastic sheet, broken intopieces, and ground to about 8 mesh with an Abb cutter. Exactly 200 gramsof this molding powder was placed in a glass-top quart jar with the topin place but not sealed. The jar and its contents were heated for 16hours at 100 C; in an oven. From this moldin P wder a plastic disc 2%inches in diameter and 0.065 inch thick was compression molded in aconventional ring and plug mold, employing 5 grams of molding powder andmolding at 2000 lbs. p. s. i. at 200 C. for 5 minutes.

'A similar molding powder and molded disc were prepared by the sameprocedure from the same flake ethyl cellulose but without anyp-secamylphenol.

Viscosity measurements were then made on the original fiake ethylcellulose, on the molded disc of ethyl cellulose plastic compositioncontaining p-sec-amylphenol and on the molded disc Timely Evaluation ofp-sec-amylphenol as stabilizer for ethyl cellulose after hightemperature milling and molding'operations Viscosity, Sample Centin isesOriginal Flake Ethyl Cellulose 1 Containing 0.35%

- Butadiene Sulione by weight 71 Ethyl Cellulose Containing .0. taneSulfone by weight in Molded Disc". 12, & Ethyl Cellulose 1 Containing0.35% Butadicne Sulfone by weight plus 2%. by weight ofp-sec-Amylplienol 111 w Molded 'Disc 1 46.4% Ethoxyl content.

These data illustrate that a small amount of p-sec-amylphenol in anethyl cellulose plastic composition which issubjected to hightemperature milling and molding operations effectively stabilizes theethyl cellulose with respect to'viscosityretention.

- The method and compositions of this inventioncall for use of celluloseethers of the thermoplastic type and of sufiicient degree ofpolymerization to yield tough. molded, articles. In gen. eral, celluloseethers soluble in any of the common organic solvents, such as acetone,benzene, toluene-alcohol, methanol, ethanol, ethyl, acetate, butylacetate, and the like, are of the required thermoplastic type. Ethylcellulose having an ethoxyl content between about 37% and about 52%,preferably between about 43% and.

about 48% and having a viscosity of at least about 20 C. P. S., isparticularly suitable. However, thermoplastic propyl cellulose, ethylpropyl cellulose, ethyl butyl cellulose, methyl ethyl cellulose, andbenzyl cellulose are likewise useful in molding compositions, and, likeethyl cellu-. lose, their molding compositions are very greatly improvedin color of the molded product by pro! ceeding in accordance with. thisinvention. It.

is desirable that the cellulose ethers be so pre.-. pared or purified asto eliminate any substantial proportion of free acid. Thus, treatmentwith strong acids should be avoided unless there is subsequentneutralization of any free acid groups by basic ions, such as sodium,calcium, magnesium, cesium, copper, and the like.

..The stabilizers according to the present in-,

aqueous alcohol and a solution of the stabilizer added to the suspensionfor absorption by the cellulose ether. Again the stabilizer may be addedduring a tumbling, stirring, or other similar operation for distributingthe stabilizer through the granular cellulose ether. Incorporation ofthe stabilizer at some stage of manufacture is desirable, since itfrequently happens that the cellulose ether is stored for considerableperiods before use, and the presence of an effective stabilizer preventsany substantial degradation due to aging.

The stabilizer may also be incorporated during preparation of theproduct in which the cellulose ether is eventually employed. Forexample, in the preparation of cellulose ether lacquers, moldingpowders, etc., the stabilizer may be added to the finished lacquer or tothe lacquer solvent during or prior to dissolving the other lacqueringredients; to the mixture of ingredients prior to or;

during formation of a molding powder, etc.

The amount of p-sec-amylphenol utilized mayvary from about 0.5% to about5.0% of the weight of the cellulose ether. Preferably, it is employedisfactory stability and other required characteristics. Larger amountsthan about 5% produce no substantial additional stabilizing effect,while amounts below about 0.5% usually do not create the desired degreeof stabilization.

When sulfur dioxide is included substantially similar amounts ofp-sec-amylphenol will be utilized in order to obtain maximum stabilitycharacteristics. Sulfur dioxide may be provided as such at the time ofmolding the cellulose ether composition containing the p-sec-amylphenol,by passing a small stream of sulfur dioxide into the molding chamber orinto a chamber or hopper by which the thermoplastic composition is ledto the molding chamber. A similar result is obtained by subjecting amolding powder of the cellulose ether composition to an atmosphere ofsulfur dioxide, whereby it absorbs some of the sulfur dioxide, and thenmolding the composition by compression, injection, or extrusion underheat before the absorbed sulfur dioxide has been lost- Usually it ismore convenient to incorporate in the molding composition a compoundwhich will decompose at the molding temperature to form sulfur dioxide,and p-sec-amylphenol, and then molding the composition under heat.Temperatures utilized in molding will be at least sufficient to causerelease of sulfur dioxide from the. particular compound used. Generallythese will be of the order of about 200 (7., although temperatures above.or below this figure may be used. By this method, a small amount ofsulfur dioxide is released under the heat of the molding operation.Thus, there is provided a thermoplastic cellulose ether moldingcomposition containing both the compound capable of releasing sulfurdioxide and the psec-amylphenol. Such a com-.. position is capable ofbeing molded to strong, tough articles which may be of pale color or apastel shade or of very greatly reduced color in the case of cleararticles.

The sulfur dioxide-releasiug compound may be incorporated in thecellulose ether at the time it is manufactured, or it may beincorporated during the preparation of the molding composition. Eitherof the latter procedures has the advantage of providing the celluloseether with a color protective influence during the milling needed toform a molding powder.

Any compound which is substantially colorles. which does not discolorunder heat, and which does not in itself function as an acid strongerthan sulfurous acid is suitable. The sulfones of aliphatic compounds,such as those derived from butadiene, piperylene, isoprene, 2-methylpentadiene, amyldiene, or other diene hydrocarbons, are particularlyuseful since they release sulfur dioxide freely at 200 C. withoutleaving any ap-. preciable residue. Polypropylenesulfone,'polyalkylpolysulfones generally, and cyclic dipropylene sulfoneare effective. Aliphatic sulfonates provide another group of compoundswhich, in most cases, give off sulfur dioxide at 200 C.; such sulfonatesas sodium sulfodiethyl succinatasodium sulfodipropyl succinate, sodiumsulfodibutyl succinate, sodium sulfodiamyl succinate, sodium sulfodihexyl succinate, sodium sulfodioctyl succinate, sodium sulfodilaurylsuccinate, equivalent potassium compounds, and similar derivatives ofsubstituted succinates, have been found particularly suitable since theresidue is quite compatible in the cellulose ether compositions and, infact, functions as a plasticizer. These compounds may be prepared bycondensation of solium bisulfite with the corresponding esters of maleicacid.

Any aliphatic or alicyclic sulfonate which will release sulfur dioxideupon heating is suitable. Alkyl and other organic sulfites, forexample,dim'ethyl sulfite, diethyl sulfite, dibutyl sulfite, methyl bisulfite,ethyl bisulfite, acetone bisulfite, normal-heptaldehyde bisulfite, andsodium formaldehyde sulfoxylate, were found to function by release ofsulfur dioxide at 200 C. Inorganic compounds, such as sodium bisulfite,sodium meta-bisulf1te, potassium bisulfite, calcium bisulfite, sodiumhydrosulfite, and the like, which are capable of releasing sulfurdioxide upon heating at 200 C. have also been found suitable. Theinorganic materials are of use in pale pigmented molding compositionsbut tend to add haze to compositions intended for clear moldings.

, The quantity of sulfur dioxide or sulfur dioxidereleasing materialwill, in general, be quite small but may vary considerably with theparticular compound utilized. It is most easily expressed on the basisof the. content of sulfur, dioxide in free or combined form, and, onthis basis,'at least about 0.005% by weight of sulfur dioxide 'based'upon the celluloseether in the molding compost tion should be presentduring the molding operation in order to obtain improvement in color ofthe molded article. Preferably, a quantity betweenabout 0.05% and about0.5% of sulfur dioxide based on the weight of the cellulose ether willbe utilized, it being understood that this amount represents only thesulfur dioxide content of the actual compound present. In general, nogmore than about 0.2% of sulfur dioxide in loosely combined form need bepresent, and in view of the possibility of corrosion of equipment;

by sulfur dioxide, no more than this amount will ordinarily be used. Inany case, no more than 2 of combined or free sulfur dioxide should beused because of development of objectionable odor and degradation,scorching, etc. in the finished plastic.

Where gaseous sulfur dioxide is used, only a small amount need be passedthrough the mold-.- ing composition as absorption of only very smallamounts is needed. Where butadiene sulfone is used, 0.2 to 0.5% on theweight of the cellulose ether (equivalent to 0.11% to 0.27% sulfurdioxide) is an optimum quantity, some of thesulfur dioxide beingreleased in milling to form molding powder and the remainder, or some ofthe re-., mainder, being released in molding. However,

0.01% to 2.0% of the sulfone, based On the cel-...

positions, and uses, the optimum quantities wili a .c ns ee r It will beunderstood that plasticizers, suchlas dibutyl phthalate, diethylphthalate, butyl stear ate, triphenyl phosphate, tricresyl phosphate,raw castor oil, nonvolatile mineral oils, methyl phthalyl ethylglycolate, hydrogenated methyl abietate, and the like, may beincorporated with the cellulose ether as usual in the preparation ofplastic masses. oil-soluble phenol aldehyde condensates. ester gum,hydrogenated glycerol abietate, pentaerythritol abietate, rosin, andoil-modified alkyd resins, would also be included although, as a rule,these substances are not used extensively in plastics intended formolding. 'Similarly,'wax'es, such as paraflin, microcrystallinepetroleum waxes, carnauba wax, candelilla wax, montan wax, and Japanwax, may also be included. Pigments, dyes, and fillers may also beincluded.

The method in accordance with this invention includes shaping with theaid of heat b-y-any mechanical modification. Thus, shaping may be bycompression molding under heat, injection molding, or by extrusion,drawing, and the like; Temperatures may vary from to 300 C. Theinvention is particularly valuable in permitting molding at therelatively high but eflicient and frequently necessary temperatures ofthe order o1-1-9 0- 250 C.'

The amount may be less than;

Likewise, resins, such as the It will be l'a'ppre'ci'ated' that thecompositions .in accordancerwiththis invention are alsouseful where heatis not essential for shaping but where a p sit may. be su ect d torelatively hi h temperatures or to moderately'high temperatures forlong" periods of time. Thus, the compositions retain goodicolor andstability over long periods of exposure toheat and light" in the form oflacquer films, electrical insulation, impregnated and coated fabric, andinfilm or sheeting.

' It has been found that the compositions in a'ccordance with thisinvention can be molded at quite high temperatures without the formationof rather dark color as' normally encountered with cellulose others. Thecor'r'ipositions are also stabilized against degradation in the form ofsevere viscosity drop. Stability of this nature preserves toughness.Furthermore, the compositions are capable'o fwithstanding ultravioletlight of the type encountered in exposure to sunlight and sun lamps forlong periods without development of dark spots, discoloration, and otherdegradation. The invention permits the preparation of clear and pastelshades in thermally molded cellulose ether compositions.

Viscosities given throughout this specification are defined. in terms ofcentipoises as determined on solutions of the cellulose ether in 80:20toluenezalcohol at 25 C. The per cent viscosity retentions werecalculated by determining the Viscosities of a given sample before andafter treatment, such as heat-treatment, and dividing the latter by theformer.

The 8-1 sun lamp-fog box cycle is fully described in the Governmentpublication dated J anuary 24, 1944, and entitled Federal Specificationfor Plastics, OrganicGeneral Specifications -Test Methods under testLP406a.. The cycle includes exposure in a fog chamber for two hours, twohours irradiation under an 8-1 lamp, two hours additional exposure inthe fog chamber, followed by eighteen hours irradiation. The cycle maybe repeated any number of times.

What I claim and desire to protect by Letters Patent is:

l. A stabilized cellulose ether composition comprising a thermoplasticcellulose ether and from about 0.5% to about 5% of p-sec-amylphenol,said composition being stabilized with respect to viscosity and colorduring and after exposure to heat, light, oxidation, and weathering byvirtue of the presence therein of said p-sec-amylphenol.

2. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose and from about 0.5% to about 5% of p-sec-amylphenol,said composition being stabilized with respect to viscosity and colorduring and after exposure to heat, light, oxidation, and Weathering byvirtue of the presence therein of said p-sec-amylphenol.

3. A stabilized cellulose ether composition comprising a thermoplasticcellulose ether, a sulfur dioxide-producing compound which issubstantially colorless, which does not discolor under heat, which doesnot in itself function as an acid stronger than sulfurous acid and whichreleases sulfur dioxide at 200 C., in an amount between about 0.005% andabout 0.5% of the weight of the cellulose ether on the basis of thecontent of combined sulfur dioxide, and from about 0.5% to about 5% ofp-sec-amylphenol, said composition being stabilized with respect toviscosity and color during and after exposure to heat, light, oxidation,and weathering by virtue of the presence therein of saidp-sec-amylphenol and said sulfur dioxide-releasing compound.

'4. Astabllized cellulose ether composition com.- prlsln'g athermoplasticv ethyl cellulose; an allfphatic die'ne sulfone which issubstantially colorless, which does not discolor under heat, which doesnot in itself function as an acid stronger than sulfurous acid and whichreleases sulfur dioxide at 200 (3., in an amount between about 0.005%andabout 0.5% of the weight of the ethyl cellulose on'the basic of thecontent of combined sulfur dioxide, and from about 0.5% to about 5% ofp-sec-amylphenol, said composition being stabilized with respect toviscosity and color during and after exposure to heat, light, oxidation,and weathering by virtue of the presence therein of said'p-sec-amy-lphenol and said sulfur dioxide-releasing compound.

' 5. A stabilized cellulose ether composition com prising athermoplastic ethyl cellulose, butadiene sulfone in an amountbetween'about 0.01% and about 2.0% of the weight of the ethyl cellulose,and from about'0.5% to about 5% of p-secamylphenol, said compositionbeing stabilized with respect to viscosity and color during and afterexposure to heat, light, oxidation, and weathering by virtue of thepresence therein of said p-sec-amylphenol and said butadiene sulfone.

6. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, a sulfodialkyl succinate which is substantiallycolorless, which does not discolor under heat, which does not in itselffunction as an acid stronger than sulfurous acid and which releasessulfur dioxide at 200 C., in an amount between about 0.005% and about0.29% of the weight of the ethyl cellulose on the basis of the contentof combined sulfur dioxide, and from about 0.5% to about 5% ofp-sec-amylphenol, said composition being stabilized with respect toviscosity and color during and after exposure to heat, light, oxidation,

and weathering by virtue of the presence therein of saidp-sec-amylphenol and said sulfur dioxidereleasing compound.

'7. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, sodium sulfodioctyl succinate in an amount betweenabout 0.05% and about 4.0% of the weight of the ethyl cellulose, andfrom about 0.5% to about 5% of p-sec-amylphenol, said composition beingstabilized with respect to viscosity and color during and after exposureto heat, light, oxidation, and weathering by virtue of the presencetherein of said p-sec-amylphenol and said sodium sulfodioctyl succinate.

8. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, an organic sulfite which is substantially colorless,which does not discolor under heat, which does not in itself function asan acid stronger than sulfurous acid and which releases sulfur dioxideat 200 (3., in an amount between about 0.005%' and about 0.5% of theweight of the ethyl cellulose on the basis of the content of combinedsulfur dioxide, and from about 0.5% to about 5% of p sec-amylphenol,said composition being stabilized with respect to viscosity and colorduring and after exposure to heat, light, oxidation, and weathering byvirtue of the presence therein of said p-sec-amylphenol and said sulfurdioxidereleasing compound.

9. Astabilized cellulose ether composition comprising-a thermoplasticethyl cellulose, diethyl sulfite in an amount between about 0.005% andabout 0.5% of the weight of the ethyl cellulose on the basis of thecontent of combined sulfur dioxide, andfrom about 0.5% to about 5% 'ofp-secamylphenol, said composition being stabilized with respect toviscosity and color during and "after exposure to heat, light,oxidation, and

-;weathering by virtue of the presence therein of said p-sec-amylphenoland said diethylsulfite.

weight of the cellulose ether on the basis of the content of combinedsulfur dioxide, and from about 0.5% to about 5% of p sec-amylphenol,

said composition being stabilized with respect to ."viscosity and colorduring and after exposure to heat, light, oxidation, and weathering byvirtue of the presence therein of said p-sec-amyl- ;phenol and saidsulfur dioxide-releasing compound. WILLIAM KOCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Number 1:, 741,975 361,341

UNITED STATES PATENTS Name Date Macht Mar. 1,1938 Bachman Mar. 10, 1942Dreyfus Aug. 1, 1944 Swan et al. Sept. 3, 1946 Myles Mar. 29, 1949FOREIGN PATENTS Country Date France Feb. 24, 1933 Great Britain Nov. 16,1931 OTHER REFERENCES Staudinger, of; (1935),1). 458.

Ber. der Deut. Chem. Ges.

Bacher et al., Rec. des Trav. Chim. des Pay- Bas (1935), pp. 538 to 544.

1. A STABILIZED CELLULOSE ETHER COMPOSITION COMPRISING A THERMOPLASTICCELLULOSE ETHER AND FROM ABOUT 0.5% TO ABOUT 5% OF P-SEC-AMYLPHENOL,SAID COMPOSITION BEING STABILIZED WITH RESPECT TO VISCOSITY AND COLORDURING AND AFTER EXPOSURE TO HEAT, LIGHT, OXIDATION, AND WEATHERING BYVIRTUE OF THE PRESENCE THEREIN OF SAID P-SEC-AMYLPHENOL.